U.S. patent number 5,401,305 [Application Number 08/104,125] was granted by the patent office on 1995-03-28 for coating composition for glass.
This patent grant is currently assigned to Elf Atochem North America, Inc.. Invention is credited to Ryan R. Dirkx, Glenn P. Florczak, David A. Russo.
United States Patent |
5,401,305 |
Russo , et al. |
March 28, 1995 |
Coating composition for glass
Abstract
A composition for coating glass by chemical-vapor deposition
comprises a mixture of a tin oxide precursor monobutyltin
trichloride, a silicon dioxide precursor tetraethylorthosilicate,
and an accelerant such as triethyl phosphite; the composition is
gaseous below 200.degree. C., and permits coating glass having a
temperature from 450.degree. to 650.degree. C. at deposition rates
higher than 350 .ANG./sec. The layer of material deposited can be
combined with other layers to produce an article with specific
properties such as controlled emissivity, refractive index,
abrasion resistance, or appearance.
Inventors: |
Russo; David A. (Norristown,
PA), Dirkx; Ryan R. (Glenmoore, PA), Florczak; Glenn
P. (East Brunswick, NJ) |
Assignee: |
Elf Atochem North America, Inc.
(Philadelphia, PA)
|
Family
ID: |
27123834 |
Appl.
No.: |
08/104,125 |
Filed: |
December 13, 1993 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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814366 |
Dec 26, 1991 |
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814352 |
Dec 27, 1991 |
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Current U.S.
Class: |
106/287.1;
106/287.14; 106/287.13; 106/287.16; 106/287.15 |
Current CPC
Class: |
C23C
16/40 (20130101); C03C 17/2453 (20130101); C03C
17/3417 (20130101); C03C 2217/91 (20130101); C03C
2218/1525 (20130101); C03C 2217/23 (20130101) |
Current International
Class: |
C03C
17/245 (20060101); C03C 17/23 (20060101); C03C
17/34 (20060101); B32B 17/06 (20060101); C23C
16/40 (20060101); C09D 005/00 () |
Field of
Search: |
;106/287.13,287.14,287.15,287.16,287.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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57-34164 |
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Feb 1982 |
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JP |
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58-189263 |
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Apr 1983 |
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JP |
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833649 |
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Jun 1981 |
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SU |
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Primary Examiner: Brunsman; David
Attorney, Agent or Firm: Marcus; Stanley A.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of our U.S. patent
applications, Ser. Nos. 07/814,366, now abandoned, filed Dec. 26,
1991, and 07/814,352, now abandoned, filed Dec. 27, 1991, and a PCT
national stage filing under 35 U.S.C. 371 of PCT/US92/10873.
Claims
What is claimed is:
1. A gaseous composition at a temperature below about 200.degree.
C. at atmospheric pressure, adapted to deposit at least a first
layer of tin oxide and silicon oxide onto glass at a rate of
deposition greater than about 350 .ANG./sec. wherein the
composition comprises a precursor of tin oxide, a precursor of
silicon oxide of formula R.sub.m O.sub.n Si.sub.p, where m is from
3 to 8, n is from 1 to 4, p is from 1 to 4, and R is independently
chosen from hydrogen and acyl, straight, cyclic, or branched-chain
alkyl and substituted alkyl or alkenyl of from one to about six
carbons, and phenyl or substituted phenyl, an accelerant selected
from the group consisting of organic phosphites, organic borates
and water, and mixtures thereof, and a source of oxygen.
2. The gaseous composition of claim 1, adapted to deposit at least
a first layer comprising tin oxide and silicon oxide onto
transparent flat glass at a temperature of from 450.degree. to
about 650.degree. C.
3. The gaseous composition of claim 1, adapted to deposit at least
a first layer comprising tin oxide and silicon oxide onto
transparent flat glass to produce a glass article having
essentially no reflected color in daylight.
4. The gaseous composition of claim 1 adapted to continuously
deposit at least a first layer of tin oxide and silicon oxide onto
a continuously moving transparent flat glass substrate.
5. The composition of claim 1 at a temperature below about
175.degree. C.
6. The composition of claim 1 wherein the organic phosphite and
organic borate accelerants have the formula (R"O).sub.3 P and
(R"O).sub.3 B where R" is independently chosen from straight,
cyclic or branched-chain alkyl or alkenyl of from one to about six
carbons; phenyl, substituted phenyl, or R'" CH.sub.2 CH.sub.2 --,
where R'" is MeO.sub.2 C--, EtO.sub.2 C--, CH.sub.3 CO--, or
HOOC--.
7. The composition of claim 1 wherein the precursor of the tin
oxide is R.sub.n SnX.sub.4-n, where R is a straight, cyclic, or
branched-chain alkyl, or alkenyl of from one to about six carbons;
phenyl, substituted phenyl, or R'CH.sub.2 CH.sub.2 --, where R' is
MeO.sub.2 C--, EtO.sub.2 C--, CH.sub.3 CO--, or HO.sub.2 C--; X is
selected from the group consisting of halogen, acetate,
perfluoroacetate, and their mixtures; and where n is 0, 1, or
2.
8. The composition of claim 1 wherein the precursor of the tin
oxide is an alkyltin halide.
9. The composition of claim 1 wherein the precursor of the tin
oxide is an alkyltin chloride.
10. The composition of claim 1 wherein the precursor of the tin
oxide is chosen from the group consisting of monobutylytin
trichloride, dibutylytin dichloride, tributylytin chloride, and tin
tetrachloride.
11. The composition of claim 1 wherein the precursor of silicon
oxide is selected from the group consisting of
tetraethylorthosilicate, diacetoxydi-t-butoxysilane,
ethyltriacetoxysilane, methyltriacetoxysilane,
methyldiacetoxylsilane, tetramethyldisiloxane,
tetraramethylcyclotetrasiloxane, dipinacoloxysilane,
1,1-dimethylsila-2-oxacyclohexane, tetrakis (1-methoxy-2-propoxy)
silane, and triethoxysilane.
12. The composition of claim 1 wherein the precursor of silicon
oxide is tetraethylorthosilicate.
13. The composition of claim 1 wherein the accelerant comprises
triethyl phosphite.
14. The composition of claim 1 wherein the accelerant comprises
triethyl phosphite and triethyl borate.
15. The gaseous composition of claim 1 adapted to deposit at least
a first layer of tin oxide and silicon oxide onto glass at a rate
of deposition greater than about 400 .ANG./sec.
16. The gaseous composition of claim 1 adapted to deposit at least
a first amorphous layer of tin oxide and silicon oxide onto
glass.
17. The gaseous composition of claim 1 adapted to deposit a
plurality of layers comprising tin oxide and silicon oxide onto
glass, the outermost layer of which is further adapted for deposit
of at least a second layer.
18. The composition of claim 17 adapted to deposit a plurality of
layers comprising tin oxide and silicon oxide onto glass, the
outermost layer of which is further adapted for deposit of a layer
comprising tin oxide.
19. The composition of claim 17 adapted to deposit a plurality of
layers comprising tin oxide and silicon oxide onto glass the
outermost layer of which is further adapted for deposit of a layer
comprising tin oxide and fluorine.
20. The composition of claim 17 wherein the second layer comprises
a doped tin oxide.
21. The composition of claim 17 wherein said plurality of layers
are deposited from a precursor mixture comprising monobutyltin
trichloride, tetraethyl orthosilicate and triethyl phosphite.
22. The composition of claim 1 adapted to deposit at least a first
layer comprising tin oxide and silicon oxide onto glass, said first
layer having a refractive index which changes continuously between
the glass substrate and the top of the layer.
23. A gaseous composition at a temperature below about 200.degree.
C. at atmospheric pressure, adapted to deposit at least a first
amphorous layer comprising tin oxide and silicon oxide onto glass
at a rate of deposition greater than about 400 .ANG./sec., the
layer having a controlled index of refraction, wherein the
composition comprises a tin oxide precursor, a silicon oxide
precursor of formula R.sub.m O.sub.n Si.sub.p, where m is from 3 to
8, n is from 1 to 4, p is from 1 to 4, and R is independently
chosen from hydrogen and acyl, straight, cyclic, or branched-chain
alkyl and substituted alkyl or alkenyl of from one to about six
carbons, and phenyl or substituted phenyl, and at least one
accelerant chosen from the group consisting of boron and
phosphorous esters and water.
24. The gaseous composition of claim 23 adapted to continuously
deposit at least a first layer comprising tin oxide and silicon
oxide onto a continuously moving flat glass substrate at a
temperature of from about 450.degree. to about 650.degree. C., and
comprising monobutyltin trichloride, tetraethyl orthosilicate and
an accelerant.
25. A gaseous composition at a temperature below about 200.degree.
C. and at atmospheric pressure, adapted to deposit at least a first
layer comprising amorphous tin oxide and silicon oxide onto glass
at a temperature of front about 450.degree. to 650.degree. C. at a
rate of deposition greater than about 350 .ANG./sec., wherein the
composition comprises:
a tin oxide precursor of formula R.sub.n SnX.sub.4-n, where R is a
straight, cyclic, or branched-chain alkyl, or alkenyl of from one
to about six carbons; phenyl, substituted phenyl, or R'CH.sub.2
CH.sub.2 --, where R' is MeO.sub.2 C--, EtO.sub.2 C--, CH.sub.3
CO--, or HO.sub.2 C--; X is selected from the group consisting of
halogen, acetate;, perfluoroacetate, and their mixtures; and where
n is 0, 1, or2;
a silicon oxide precursor of formula R.sub.m O.sub.n Si.sub.p,
where m is from 3 to 8, n is from 1 to 4, p is from 1 to 4, and R
is independently chosen from hydrogen and acyl, straight, cyclic,
or branched-chain alkyl and substituted alkyl or alkenyl of from
one to about six carbons, and phenyl or substituted phenyl;
one or more accelerants selected from the group consisting of water
and organic phosphites and organic borates of formula (R"O).sub.3 P
and (R"O).sub.3 B where R" is independently chosen from straight,
cyclic or branched-chain alkyl or alkenyl of from one to about six
carbons; phenyl, substituted pheny, or R'" CH.sub.2 CH.sub.2 --,
where R'" is MeO.sub.2 C--, EtO.sub.2 C--, CH.sub.3 CO--, or
HOOC--; and
a source of oxygen.
26. A composition according to claim 25 in which the precursor of
the tin oxide is an alkyltin halide, the precursor of the silicon
oxide is tetraethylorthosilicate, diacetoxydi-t-butoxysilane,
ethyltriacetoxysilane, methyltriacetoxysilane,
methyldiacetoxylsilane, tetramethyldisiloxane,
tetramethylcyclotetrasiloxane, dipinacoloxysilane,
1,1-dimethylsila-2-oxacyclohexane, tetrakis (1-methoxy-2-propoxy)
silane, or triethoxysilane, and the accelerant comprises one or
both of triethyl phosphite and triethyl borate.
27. A composition according to claim 26 in which the tin oxide
precursor comprises monobutyltin trichloride, the silicon oxide
precursor comprises tetraethyl orthosilicate and the accelerant
comprises triethyl phosphite.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is in the field of coatings on substrates.
More particularly, this invention is in the field of compositions
for the deposition of coatings at high rates on glass or glass
articles to provide controlled refractive index, improved
emissivity characteristics, and/or appearance and abrasion
resistance, and to complement or enhance other properties.
2. Description of the Prior Art
Transparent semi-conductor films such as indium oxide, cadmium
stannate, or doped tin oxide, can be applied to various transparent
substrates such as, e.g., soda-lime glasses, in order to reflect
long-wavelength infrared radiation. Transparent dielectric films
such as titanium dioxide or undoped tin oxide can be applied to
transparent articles such as glass bottles to form a base coat for
a second coating with a specific function. Depending on the
thickness of the semiconductor or dielectric film, various
reflected iridescent colors may be observed. This iridescent effect
is considered to be detrimental to the appearence of the glass in
applications such as windows with low emissivity, or bottles for
food or beverages.
Methods and apparatus for coating glass, and especially continuous
coating on moving glass, are known in the art. A description of
apparatus useful in preparing a coated-glass, article is found in
Lindner, U.S. Pat. No. 4,928,627, made a part of this disclosure by
reference herein.
Various procedures have been devised for reducing or eliminating
iridescence. For the low-emissivity application, Zaromb, in U.S.
Pat. No. 3,378,396, describes an article comprising a transparent
glass substrate coated with tin and silicon oxides; the coating
varies gradually in composition from a high ratio of silicon oxide
to tin oxide: at the substrate surface, gradually changing to
almost pure tin oxide, and changing further to a ratio of not more
than 60% silicon oxide to not less than 40% tin oxide at the
interface of that coating with the atmosphere. The refractive index
of the coating nearest to the substrate is about 1.5, substantially
the refractive index of silica glass, and changes to about 2.0, the
refractive index of tin oxide, at the air interface, providing an
intermediate coating layer without an optical interface. The
article so coated has little to no iridescence in reflected light.
Zaromb teaches that aqueous solutions of tin and silicon chlorides
can be spray-applied to achieve his coatings. Spray applications
are usually batch operations which do not yield high-quality,
uniform films; there is no mention of other means of application
such as chemical-vapor deposition (CVD). He also fails to give any
indication of the deposition rate, a key parameter for a commercial
industrial application.
Another approach is described by Gordon in U.S. Pat. No. 4,187,336.
One or more layers of a transparent material with a refractive
index intermediate between that of a glass substrate and a
conductive tin oxide film are deposited by atmospheric-pressure CVD
between the glass and the tin oxide film. It is necessary for the
intermediate layers to have specific refractive indices and
thicknesses in order to be effective. It is noted that when the
intermediate films contained silicon dioxide, suitable volatile
compounds were found to be silane, dimethysilane, diethylsilane,
tetramethyl silane, and the silicon halides. No other precursors
are mentioned. The deposition rates obtained for the processes
described were on the order of from 10 to 20 Angstroms per second
(.ANG./sec.). Such rates are an order of magnitude below those
necessary for a commercial industrial process.
In U.S. Pat. No. 4,206,252, Gordon describes a process for
depositing mixed oxide and nitride coating layers of continuously
varying refractive index between a glass substrate and an
infra-red-reflecting coating, whereby the film iridesence is
eliminated. When silicon dioxide is part of the mixed oxide film,
the patent teaches that volatile silicon compounds with Si--Si and
Si--H bonds are suitable precursors. Compounds such as
1,1,2,2-tetramethyldisilane, 1,1,2-trimethyldisilane, and
1,2-dimethyldisilane are disclosed. All of the compounds containing
Si-Si and Si-H bonds to which reference is made are expensive, and
none are comercially available.
In U.S. Pat. No. 4,386,117, Gordon describes a process for
preparing mixed silicon oxide/tin oxide coatings all specific
refractive indices or a continuous gradient as taught by Zaromb in
U.S. Pat. No. 3,378,396, at optimum deposition rates of 80 to 125
.ANG./sec, using alkoxy-peralkylpolysilane precursors such as
methoxypentamethyldisilane or dimethoxytetramethyldisilane. Again,
the silica precursors cited and inferred are impractical for
industrial use, because none of them is commercially available on a
large scale.
Lagendijk, in U.S. Pat. No. 5,028,566, notes in column 4 that
tetraethyl orthosilicate (TEOS) suffers from a number of
disadvantages in its application to a substrate by low-.pressure
CVD; that is, a pressure of about 500 milliTorr. These
disadvantages include difficulty of doping the resultant film with
phosphorus, and controlled-source delivery due to the low vapor
pressure of TEOS. Lagendijk also points out that attempts at an
all-liquid process to produce borophosphosilicate glass have met
with limited success. He further equates the dopant effect within a
broad range of phosphorus, boron, antimony, arsenic and chromium
compounds, but only when used with silicon compounds having no
carbon-oxygen-silicon bonds, and two or more silicon atoms.
In bottle applications, the coatings are applied at such low
thicknesses, i.e., about 100 .ANG., that no iridescence is
possible. However, the films are not continuous, and this
discontinuity makes them unsuitable for other applications. One
solution to the, discontinuity is to deposit thicker films of a
material with a refractive index closer to that of the article. A
mixed metal oxide/silicon oxide material deposited at a
significantly more rapid rate than has heretofore been achieved
would be desirable, as discussed further hereinbelow.
All the silanes disclosed in the prior art for making mixed metal
oxide/silicon dioxide coatings have certain features which make
them unsatisfactory for commercial development. Some are very
corrosive, flammable, or oxygen-sensitive, and require special
handling. Others are not readily available, or are too expensive
for commercial use. Of the materials which can be used, the biggest
problem which limits their commercial development in mixed metal
oxide/silicon oxide and/or axynitride intermediate layers has been
that of inadequate deposition rates. When the substrate is flat
glass and the deposition process is CVD at ambient pressure, the
deposition rate of the intermediate layers must be high enough to
coat a production-line glass ribbon traveling at line speeds as
high as about 15 meters per minute (m/min). Rates for deposition of
the desired layers of about 350 .ANG. are desirable, and rates on
the order of 400 to 600 .ANG./sec are preferable. Such rates have
not heretofore been achieved under conditions which permit
continuous, mass production of glass with properties.
To overcome the problems as discussed hereinabove, silica
precursors are needed which are inexpensive, readily available,
easy to handle, and have adequate deposition rates when vaporized
with metal oxide precursors. Alkoxysilanes such as TEOS, a
commodity chemical, would be desirable. However, prior to the
present invention, it has not been possible to deposit silicon
oxide films from TEOS by atmospheric-pressure CVD at commercially
acceptable deposition rates, except at temperatures at or above 700
degrees Celsius (.degree.C.). Some success has been achieved at
temperatures of from about 450.degree. to about 680.degree. C., but
only by modifying the atmospheric-pressure CVD process through
plasma enhancement or reduced pressure, neither of which is
generally acceptable for commerical use on a continuous glass
ribbon. Additives such as oxygen, ozone, or trimethyl phosphite
have also been used in these modified processes, but the rates
achieved are still lower than those needed for an effective
commercial system.
D. S. Williams and E. A. Dein, in J. Electrochem. Soc. 134(3)
657-64 (1987), showed that phosphosilicate and borophosphosilicate
glass films with controllable refractive index can be deposited at
rates of about 200 .ANG./sec between 515.degree. and 680.degree. C.
by the low-pressure CVD of TEOS with phosphorous or boron oxides in
concentrations which varied as a function of the additive used. The
low-pressure process described here is not amenable to a continuous
on-line application of oxides.
In Proceedings, 2.sup.nd International ULSI Science and Technical
Symposium, ECS Proceedings Vol. 98(9), 571-78 (1989), D. A. Webb et
al. reported that silicon oxide films could be deposited from TEOS
at rates of about 125 .ANG./sec in a plasma-enhanced CVD process
using oxygen. However, plasma-enhanced CVD is not a viable option
for the continuous commmercial application of oxide films to glass,
being a batch process requiring complex and costly low-pressure
apparatus.
A. K. Hochberg and D. L. O'Meara in J. Electrochem. Soc. 136(6)
1843 (1989) reported enhanced deposition of silicon oxide films at
570.degree. C. by CVD at low pressure when trimethylphosphite was
added to TEOS. As with plasma-enhanced CVD, however, low-pressure
CVD is not readily utilized for the continuous commercial
application of silicon-oxide films on a moving glass sheet to
produce a coated-glass article, due at least in part to the cost
and complexity of the device used for deposition at low
pressure.
From a review of the prior art, it cannot be determined what
precursor combinations, if any, can be used for continuous
deposition, under conditions and at a rate suitable for mass
production, of mixed metal oxide/silicon oxide films at adequate
rates from readily available and relatively inexpensive
reagents.
Primary or secondary coatings on glass substrates are further
useful to enhance or complement properties of either the substrate
or one or more of the coatings thereon, improvement of iridesence
being only one application. Other uses of coatings include, e.g.,
protection of the substrate surface from abrasion, addition of
color to clear glass, and screening of particular wavelengths of
incident radiation.
DISCUSSION OF THE INVENTION
This invention is a gaseous composition for producing an improved
coating on glass, wherein the coated glass exhibits specific
properties such as, e.g., controlled refractive index, abrasion
resistance, color enhancement, low emissivity, selective light
filtration, and anti-iridescence on flat-glass substrates. The
invention is made by CVD at rates greater than about 350 .ANG./sec.
at atmospheric pressure and at temperatures lower than 700.degree.
C., by using a mixture which includes at least one precursor for a
metal oxide, selected from the group consisting of volatile
compounds of tin, germanium, titanium, aluminum, zirconium, zinc,
indium, cadmium, hafnium, tungsten, vanadium, chromium, molybdenum,
iridium, nickel and tantalum. The gaseous composition further
includes a precursor for silicon dioxide, and one or more additives
selected from the group consisting of phosphites, borates, water,
alkyl phosphine, arsine and borane derivatives; PH.sub.3, AsH.sub.3
and B.sub.2 H.sub.6 ; and O.sub.2, N.sub.2 O, NF.sub.3, NO.sub.2
and CO.sub.2. The additives are termed "accelerants" herein; the
accelerants serve to increase the rate of deposition of the film
onto the glass from the mixture. The mixture of precursors and
additives is gaseous under the conditions of application required
to produce the coated-glass article; the reaction of the materials
in the gaseous mixture with atmospheric or added oxygen provides
the corresponding oxides which are deposited on the glass
substrate.
Those skilled in the art will understand that precursors and
materials discussed in this specification must be sufficiently
volatile, alone or with other materials, and sufficiently stable
under the conditions of deposition, to be a part of the composition
from which the desired films are deposited.
Precursors for deposition of metal oxides include, e.g., aluminum
alkyls and alkoxides, cadmium alkyls, germanium halides and
alkoxides, indium alkyls, titanium halides, zinc alkyls, and
zirconium alkoxides. Specific examples of such compounds include,
e.g., Al(C.sub.2 H.sub.5).sub.3, CrO.sub.2 Cl.sub.2, GeBr.sub.4,
Ti(OC.sub.3 H.sub.7).sub.4, TiCl.sub.4, TiBr.sub.4, Ti(C.sub.5
H.sub.7 O.sub.2).sub.4, Zr(OC.sub.5 H.sub.9).sub.4, Ni(CO).sub.4,
VCl.sub.4, Zn(CH.sub.3).sub.2, Zr(C.sub.5 H.sub.9 O).sub.4, and the
like.
Tin precursors include those described by the general formula
R.sub.n SnX.sub.4-n, where R is independently chosen from straight,
cyclic, or branched-chain alkyl or alkenyl of from one to about six
carbons; phenyl, substituted phenyl, or R'CH.sub.2 CH.sub.2 --,
where R' is MeO.sub.2 C--, EtO.sub.2 C--, CH.sub.3 CO--, or
HO.sub.2 C--; X is selected from the group consisting of halogen,
acetate, perfluoroacetate, and their mixtures; and where n is 0, 1,
or 2. Preferred precursors for tin oxide in the article of this
invention are the organotin halides.
Precursors for silicon oxide include those described by the general
formula R.sub.m O.sub.n Si.sub.p, where m is from 3 to 8, n is from
1 to 4, p is from 1 to 4, and R is independently chosen from
hydrogen and acyl, straight, cyclic, or branched-chain alkyl and
substituted alkyl or alkenyl of from one to about six carbons, and
phenyl or substituted phenyl. Preferred precursors for silicon
oxide include tetraethylorthosilicate, diacetoxydi-t-butoxysilane,
ethyltriacetoxysilane, methyltriacetoxysilane,
methyldiacetoxylsilane, tetramethyldisiloxane,
tetramethylcyclotetrasiloxane, dipinacoloxysilane,
1,1-dimethylsila-2-oxacyclohexane, tetrakis (1-methoxy-2-propoxy)
silane, and triethoxysilane.
Suitable accelerants include phosphite and borate derivatives of
the general formula (R"O).sub.3 P and (R"O).sub.3 B, where R" is
independently chosen from straight, cyclic, or branched-chain alkyl
or alkenyl of from one to about six carbons; phenyl, substituted
phenyl, or R'"CH.sub.2 CH.sub.2 --, where R'" is MeO.sub.2 C--,
EtO.sub.2 C--, CH.sub.3 CO--, or HO.sub.2 C--; R" is preferably
alkyl or alkenyl of from 1 to 4 carbons in length. Particularly
preferred accelerants are those selected from the group consisting
of boron and phosphorus esters; most preferred are TEB and TEP.
The precursors to the overcoated layer comprise MBTC or any of the
organotins described by the general formula R.sub.n SnX.sub.4-n
above, and a material chosen to impart a semi-conductive property
to the tin oxide; such materials include, e.g., antimony compounds
such as trimethylantimony, phosphorous compounds such as
triethylphosphine, and fluorine-containing compounds such as
trifluoroacetic acid, trifiuoroacetic anhydride, ethyl
trifluoroacetate, 2,2,2-trifluoroethanol, ethyl
4,4,4-trifluoroacetoacetone, heptafluorobutyryl chloride, and
hydrogen fluoride. The tin oxide layer can also be made conductive
by depositing sub-stoiehiometric films having the composition
SnO.sub.2-x, wherein x is a non-integer having a value between zero
and 1, and wherein the value of x can vary within a given film. The
materials for imparting semi-conductive properties to the tin oxide
can also be added to the precursors for the first layer, to enhance
the emissivity of the entire coating system, i.e., the emissivity
of the combined first and second layers.
Those skilled in the art will realize that the tin oxide can be
replaced in these films entirely or in part by the oxides of other
metals such as, e.g., germanium, titanium, aluminum, zirconium,
zinc, indium, cadmium, hafnium, tungsten, vanadium, chromium,
molybdenum, iridium, nickel and tantalum.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiment of the present invention is a gaseous
composition at a temperature below about 200.degree. C. at
atmospheric pressure, adapted to deposit a film of tin ,oxide and
silicon oxide at a rate greater than about 350 .ANG./sec. which
comprises a precursor of tin oxide, a precursor of silicon oxide,
an accelerant selected from the group consisting of organic
phosphites, organic borates and water, and mixtures thereof, and a
source of oxygen.
In another embodiment of this invention, the composition results in
a film deposited at atmospheric pressure wherein the film comprises
one or more mixed metal oxide/silicon dioxide films on a glass
substrate, the deposition being made from a mixture comprising a
metal oxide precursor, a silicon dioxide precursor, and at least
one additive which improves or accelerates the deposition rate
significantly when compared to the deposition rate without the
additive. The deposited films can contain additional oxides related
to the additives used. Further, the deposited mixed oxide films can
have specific properties in their own right such as, e.g., designed
refractive index, or can be combined with other films, under- or
overcoated, or both, to have a combined property such as, e.g.,
color neutrality or lubricity.
In a more-preferred embodiment, the composition provides a mixed
metal oxide/silicon dioxide film comprising multiple tin
oxide/silicon dioxide layers of, e.g., increasing refractive index;
further, a chosen property of a given layer, such as, e.g., the
refractive index, can vary continuously such that an overcoated
layer of tin oxide will have minimal reflected color. A given layer
may thus have a concentration of silicon oxide and tin oxide
different from the concentrations of silicon oxide and tin oxide in
an adjacent layer. The films can also contain oxides of the
accelerants, particularly when the additives contain phosphorus or
boron.
In a most-preferred embodiment of the composition of this
invention, the precursors to the mixed oxide layer comprise
organotin halides generally and monobutyltin trichloride (MBTC) in
particular, TEOS, and the accelerant triethyl phosphite (TEP).
The compositions of the films produced by this invention were
determined by X-ray diffraction (XRD) and X-ray photoelectron
spectroscopy (XPS). The article of the present invention is
prepared by a process using accelerants whereby the process
provides a commercially acceptable continuous CVD deposition of
oxide films on moving glass, especially on a modern float-glass
line, where the batch processes of the prior art are entirely
inapplicable.
The effects of added water and added phosphites and borates on the
refractive index and deposition rate of TEOS-based mixed oxide
films are shown in the following Tables. These results are
contrasted to those in Tables IV and V, which show the effect of
the additives oxygen and a Lewis acid.
Table I shows the effect of added water. As the water concentration
is increased, regardless of the tin/silicon ratio or the gas
velocity, the deposition rate increases to commercially significant
levels. These rate increases are also accompanied by increases in
refractive index. In the tables here, the reported deposition rates
are approximate with a range of about seven percent, unless the
rate is followed by an expressed .+-. uncertainty.
TABLE I ______________________________________ Effect of Water
Concentration on Mixed Oxide Refractive Index and Deposition Rate
MBTC TEOS Water Dep. Rate mol % mol % mol % R.I. .ANG./sec
______________________________________ 665.degree. C. glass
temperature, 160.degree. C. system temperature, 50 l/min gas flow.
0.71 0.71 0.00 1.54 25 0.71 0.71 0.15 1.73 340 0.71 0.71 0.24 1.74
400 665.degree. C. glass temperature, 160.degree. C. system
temperature, 12.5 l/min gas flow. 1.05 0.59 0.00 1.74 290 1.05 0.59
0.60 1.78 330 1.05 0.59 1.10 1.80 480
______________________________________
While 160.degree. C. is preferred, the system temperature can be
from about 125.degree. to about 200.degree. C.
Table II shows the effects of added TEP and of mixtures of TEP and
lower-alkyl borate esters such as triethyl borate (TEB). The
results show that TEP is very effective in accelerating the
deposition rates of the mixed-oxide films to a high rate at
specific and controlled refractive-index values. Additions of TEB
at low levels to the TEP resulted in an additional small increase
in rate. As used in this; specification, the term "high rate," as
applied to the film deposition described herein, is greater than
about 350 .ANG./sec, and preferably about 400 .ANG./sec or higher.
All the films produced under the conditions of Table II were
clear.
TABLE II ______________________________________ Effect of
MBTC/TEOS/TEP Concentrations on Deposition Rate % Dep. Rate % TEOS
MBTC % TEP % TEB R.I. .ANG./sec
______________________________________ 0.80 0.16 -- -- 1.69 .+-.
.02 38 .+-. 3 0.80 0.11 0.76 -- 1.58 .+-. .01 542 .+-. 8 0.80 0.16
0.76 -- 1.60 .+-. .01 416 .+-. 22 0.78 1.56 0.75 -- 1.67 .+-. .01
505 .+-. 4 0.78 1.84 0.75 -- 1.69 .+-. .01 476 .+-. 45 0.28 1.56
0.36 -- 1.73 .+-. .01 231 .+-. 46 0.27 1.56 0.62 -- 1.71 .+-. .01
381 .+-. 15 0.27 1.56 0.75 -- 1.70 .+-. .01 482 .+-. 6 0.27 1.56
0.75 -- 1.70 .+-. .01 482 .+-. 16 0.27 1.56 0.74 0.18 1.70 .+-. .02
492 .+-. 13 0.79 0.16 0.76 0.19 1.59 .+-. .01 473 .+-. 56
______________________________________
The glass temperature was 665.degree. C., its speed, 0.56 m/sec;
system temperature 160.degree. C., air. MBTC, TEOS, and TEP or the
mixture of TEP and TEB were injected separately into the vaporizer
section of the coater. Each data point was the average of three
samples. The dew point was from -74.degree. to -78.degree. C.
Table III shows the effect of added oxygen. Increasing the oxygen
concentration increases the deposition rate significantly, but not
to the levels needed for commercial application.
TABLE III ______________________________________ Effect of Oxygen
Concentration On Mixed Oxide Refractive Index and Deposition Rate
MBTC TEOS Oxygen Dep. Rate mol % mol % vol % of air R.I. .ANG./sec
______________________________________ 0.71 0.71 20 1.54 25 0.71
0.71 50 1.63 50 0.71 0.71 75 1.65 160 0.71 0.71 100 1.66 240
______________________________________
665.degree. C. glass temperature, 160.degree. C. system
temperature, 50 l/min gas flow.
Table IV shows the effect of added Lewis acid, which in this case
is excess MBTC. As the concentration increases, the rate increases,
although not to the levels needed for commercial application.
TABLE IV ______________________________________ Effect of MBTC
Concentration on Mixed Oxide Refractive Index and Deposition Rate
MBTC TEOS Dep. Rate mol % mol % R.I. .ANG./sec
______________________________________ 0.48 0.47 1.78 160 0.48 +
0.23 0.48 1.78 200 0.48 + 0.47 0.47 1.85 300
______________________________________
665.degree. C. glass temperature, 160.degree. C. system
temperature, 50 l/min gas flow.
The data in the tables show that effective CVD of mixed oxide films
can be achieved at commercial rates by the present invention, with
concomitant control of refractive index. The following examples
illustrate preferred embodiments of this invention.
EXAMPLE 1
A square plate of soda-lime silica glass, 9 centimeters (cm.) on a
side, was heated on a hot block to 665.degree. C. A gas mixture of
about 0.16 mol % MBTC, 0.80 mol % TEOS, 0.75 mol % TEP, and the
balance hot air at 160.degree. C. was directed over the glass at a
rate of 12.5 liters per minute (l/min) for about 10 seconds. The
center of the glass surface was uniformly coated with a film which
had a pale green color in reflected light. Using the Prism Coupler
technique, the refractive index was found to be 1.60 and the
thickness was about 4260 .ANG., corresponding to a deposition rate
of about 426 .ANG./sec. Similarly deposited films have been shown
to be amorphous by XRD, and to be composed of oxides of tin,
silicon and phosphorus by XPS.
EXAMPLE 2
A gas mixture of about 1.84 mol % MBTC, 0.78 mol % TEOS, 0.75 mol %
TEP, and the balance hot air was directed over a glass surface in
the same manner as described in Example 1. The resulting film had a
pale magenta color in reflected light. The refractive index was
found to be 1.68, and the thickness was about 4930 .ANG.,
corresponding to a deposition rate of about 493 .ANG./sec.
Similarly deposited films have been shown to be amorphous by XRD,
and to be composed of oxides of tin, silicon and phosphorus by
XPS.
EXAMPLE 3
A gas mixture of about 1.22 mol % MBTC, 0.58 mol % TEOS, 1.09 mol %
H.sub.2 O and the balance hot air was directed over a glass surface
as described in Example 1, but for eight seconds. The resulting
film had a green color in reflected light. The refractive index was
found to be 1.78, and the film thickness was about 4650 .ANG.,
which corresponds to a deposition rate of about 580 .ANG./sec. From
XRD analysis, similarly deposited films have been found to consist
of collapsed tetragonal unit cells of tin oxide, indicating some
solid-solution formation with silicon dioxide. XPS analysis shows
that the films comprise oxides of tin and silicon.
EXAMPLE 4
Each of the films described in Examples 1 through 3 was
successively deposited for one second in ascending-index order. The
multi-layer film was then overcoated with about 3200 .ANG. of
fluorine-doped tin oxide. This film construction provided a
transparent article with essentially no reflected color under
conditions of daylight illumination.
EXAMPLE 5
A 9-cm. square of soda-lime silica glass was heated on a hot block
to 665.degree. C. A gas mixture of about 1.04 mol % MBTC in air at
160.degree. C., and a gas mixture of 1.04 mol % TEOS and 0.20 mol %
TEP in air at 160.degree. C. were directed through two
microprocessor-controlled globe valves over the glass at a total
flow rate of 12.5 l/min for 30 sec. The globe valves were
simultaneously opened and closed at a programmed rate such that the
gas composition impinging on the glass sample was continuously
changed from a mixture of high TEOS/TEP and low MBTC to a mixture
of low TEOS/TEP and high MBTC. The center of the glass surface was
uniformly coated with a film consisting of oxides of tin, silicon
and phosphorus as determined by XPS analysis. As the film thickness
increased, the amount of tin gradually increased, while the amount
of silicon and phosphorus decreased. The refractive index was
calculated from these data, and from data derived from standard
films, and found to lie between 1.52 and 1.87. This film
construction provided an article with essentially no reflected
color when overcoated with fluorine-doped tin oxide.
EXAMPLE 6
A gas mixture of about 0.16 mol % MBTC, 0.80 mol % TEOS, and the
balance hot air was directed over a glass surface as described in
Example 1 for about 60 seconds. The resulting film had a magenta
color in reflected light, and a refractive index of 1.69. The film
thickness was about 2260 .ANG., corresponding to a deposition rate
of about 38 .ANG./sec.
EXAMPLE 7
A 0.5-l clear-glass beverage bottle was rotated and heated to about
600.degree. C. in an oven over a three-minute period. The heated
bottle was transferred into a coating chamber, where it was
contacted with a vapor mixture of 0.16 mol % MBTC, 0.80 mol % TEOS,
0.75 mol % TEP, and the balance hot air at about 170.degree. C. for
10 sec. The resulting film was magenta-blue in color, and was
uniformly distributed on the sidewalls of the container from
shoulder to base. The deposition rate was estimated to be about 200
.ANG./sec from the film color, compared to about 50 .ANG./sec for
the bottle coated only with the vapor mixture of MBTC and TEOS.
From a review of the foregoing tables and examples, those skilled
in the art will realize that TEB, TEP, and water serve as
accelerants in the CVD of oxide films on glass, anti that TEP and
TEB are synergistic in accelerating the deposition rate of TEOS and
MBTC. Accelerants useful in this invention are chosen from the
group consisting of borate and phosphite esters, alkyltin halides,
and water.
While the composition of the present invention is preferably
applied continuously to a moving glass substrate by methods known
to those skilled in the art, the composition of this invention also
has utility in batch processes. In application under conditions of
continuous deposition, the composition is preferably maintained at
temperatures below about 200.degree. C., and more preferably below
about 175.degree. C., and applied to the glass moving at about 15
meters per second to provide deposition at a rate of at least 350
.ANG./sec., and preferably at a rate of at least 400 .ANG./sec.
Modifications and improvements to the preferred forms of the
invention disclosed and described herein may occur to those skilled
in the art who come to understand the principles and precepts
hereof. Accordingly, the scope of the patent to be issued hereon
should not be limited solely to the embodiments of the invention
set forth herein, but rather should be limited only by the advance
by which the invention has promoted the art.
* * * * *